title: Mutational separation of transport systems for branched-chain amino acids in Pseudomonas aeruginosa.
abstract: Several types of Pseudomonas aeruginosa mutants defective in the transport systems for branched-chain amino acids were isolated by selection for resistance to 5',5',5'-DL-trifluoroleucine, a leucine analog, under certain conditions. Mutants resistant to trifluoroleucine in the absence of Na+ were defective in the high-affinity system. These mutants fell into two classes. One class showed a defect in the production of a periplasmic binding protein for leucine, isoleucine, valine, alanine, and threonine, and the other showed normal production of the binding protein as determined by a binding assay and by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Properties of the former class of mutants have been partly described (T. Hoshino and M. Kageyama, J. Bacteriol. 141:1055-1063, 1980). Mutants selected for resistance to trifluoroleucine with Na+ and an excess amount of alanine showed a defect in the low-affinity system. Membrane vesicles prepared from such a mutant lost the transport activity for leucine. A mutant which showed increased activity of the low-affinity system with a defect in the high-affinity system was obtained from strain PML1453 (high-affinity system defective) by selecting for utilization of isoleucine as a carbon source.
mesh_terms: D000409:Alanine / Q000494:pharmacology; D000597:Amino Acids, Branched-Chain / Q000378:metabolism*; D001692:Biological Transport / Q000187:drug effects; D005798:Genes, Bacterial; D007532:Isoleucine / Q000378:metabolism; D007930:Leucine / Q000378:metabolism; D009154:Mutation; D011550:Pseudomonas aeruginosa / Q000235:genetics / Q000378:metabolism*; D012964:Sodium / Q000494:pharmacology; D014633:Valine / Q000378:metabolism
chemical_list: D000597:Amino Acids, Branched-Chain; D007532:Isoleucine; D012964:Sodium; D007930:Leucine; D014633:Valine; D000409:Alanine